Chapter 4 Precautions For Use Of Safety Programmable Controller; Precautions For Designing Safety Application; Section 4.1, Appendix - Mitsubishi Electric MELSEC-QS Series Safety Application Manual

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PRECAUTIONS FOR USE OF SAFETY
PROGRAMMABLE CONTROLLER
CHAPTER 4 PRECAUTIONS FOR USE OF SAFETY
The safety standards conformance approval must be made by the user for the entire
safety-related system.
The safety system inspection is made for the entire safety-related system including safety
components and a sequence program.
The sample program is shown in CHAPTER 5 and CHAPTER 6. However, the safety
standards approval is not obtained.
And all work for safety-related system construction (e.g. design, installation, operation,
maintenance) has to be handled by the person who has an enough education concerning
safety standards, safety devices, and safety programmable controller.
4.1

Precautions for Designing Safety Application

(1) Response time
(2) Target failure measure (PFD/PFH) calculation
PFD/PFH = A + B + C + D
Variable
A
B
B1
PROGRAMMABLE CONTROLLER
The response time is a time from the safety input off to the safety output off using the
safety programmable controller.
The response time is needed for determining the safety distance for a safety-related
system.
Calculate the response time of a system to be configured with referring to Appendix 1
and Appendix 2.
POINT
POINT
For the safety programmable controller, connecting GX Developer makes the
response time longer. Do not constantly connect GX Developer during the safety-
related system operation.
Target failure measure (PFD/PFH) is the target value of reliability for each SIL level
standardized in IEC61508.(
Calculate the target failure measure (PFD/PFH) with the following formula for each
safety function.
Calculation formula of PFD/PFH
Table 4.1 Definition of each variable
PFD/PFH of safety CPU module, safety power supply module, safety main base unit, CC-
Link Safety master module, and CC-Link IE Field Network master/local module (with safety
functions)
PFD/PFH of the CC-Link Safety remote I/O module
(1) The safety input device and safety output device are connected to the same CC-Link
Safety remote I/O module: B = B1
(2) The safety input device and safety output device are connected to the different CC-
Link Safety remote I/O modules: B = B1 + B2
PFD/PFH of the CC-Link Safety remote I/O module to which the safety input device is
connected
Section 3.4)
Definition
4.1 Precautions for Designing Safety Application
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